The present invention relates to a method and apparatus for preventing oscillation of magnetic strip material which is continuously treated while the strip is running in various processing lines such as continuous galvanizing lines, annealing lines, pickling lines and inspection lines.
In these processing lines, various treatments and inspections of the strip usually have to be conducted while the strip is running in a high line speed. For example, thickness control for the material to be coated on a strip in a continuous galvanizing line is conducted while the strip is running at a line speed of 200 m/min or more. Also, flow or thickness detections of a strip material have to be made while the strip is running.
Usually, these running strips are supported at a certain distance by a pair of rollers or pinch rollers with a tension imparting on the strip in the strip running direction. In the strip between the adjacent rollers, various types of problems arise such as oscillation in a direction of strip thickness and strip width, and also deformation of strip surfaces into a convex or concave shape. These problems become serious as the line speed of the strip increases and cause deteriorations of the strip quality due to lack of accuracy in the treatment and detection errors in the flaw inspections or thickness detections of the strip.
An object of the present invention is to provide a method and apparatus for preventing oscillation or deformation of a strip which arise in the strip while the strip is running.
According to the present invention, oscillation or deformation of a running strip can be reduced by applying a magnetic field in the direction of strip width. The magnetic field acts to attract the side edge of the strip in the direction of the magnetic field and causes a tension in the strip in the direction of the strip width, so that amplitude of strip oscillation is reduced and also bending of strip in the strip width is cured.
As a magnetic means to cause the magnetic field, any type of means to cause a magnetic field, such as permanent magnet, linear motor, solenoid, are applicable. Also any kind of strip or sheet which is made of magnetic material can be applicable to the present invention.
According to a feature of the present invention, magnetic means to produce a magnetic field is located along a passage of a running strip in the vicinity of the strip side edge in a non contacting manner so that the strip side edge is attracted to the direction of the magnetic field and a tension is imparted to the strip in the direction of the strip width. The location of the magnetic means is preferably adjusted so that a desired gap between the magnetic means and the side edge is maintained.
According to another feature of the present invention, the magnetic means is adapted for the prevention of strip oscillation in a continuous metal coating apparatus so that uniform thickness of the coating metal is advantageously obtained due to suppression of the strip oscillation. Also, by the use of the magnetic means, bending of the strip is advantageously eliminated which results in improved coating surfaces of the strip. The magnetic means is further applicable for the prevention of strip oscillation or bending other than in the continuous metal coating apparatus, such as continuous strip inspection lines.
These and further objects, features and advantages of the present invention will become more obvious from the following description when taken in connection with the accompanying drawings which show, for purposes of illustration, several embodiments in accordance with the present invention.